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copied!<p>Here's a simple desktop application that reads a <code>REG_SZ</code> value. It's crude and simple. It will read the value that you want. You may have to adapt it to Silverlight. I cannot help you there!</p> <p>I hope this is useful:</p> <pre><code>using System; using System.ComponentModel; using System.Runtime.InteropServices; using System.Text; namespace ConsoleApplication1 { internal static class NativeMethods { public const int ERROR_SUCCESS = 0; public const uint HKEY_LOCAL_MACHINE = 0x80000002; public const int KEY_READ = 0x20019; [DllImport("advapi32.dll", CharSet = CharSet.Unicode)] public static extern int RegOpenKeyEx( UIntPtr hKey, string subKey, int ulOptions, int samDesired, out UIntPtr hkResult ); [DllImport("advapi32.dll")] public static extern int RegCloseKey( UIntPtr hKey ); [DllImport("advapi32.dll", CharSet = CharSet.Unicode)] public static extern int RegQueryValueEx( UIntPtr hKey, string lpValueName, int lpReserved, IntPtr type, IntPtr lpData, ref int lpcbData ); } internal static class RegistryWrapper { private static void checkErrorCode(int errorCode) { if (errorCode != NativeMethods.ERROR_SUCCESS) throw new Win32Exception(errorCode); } public static string ReadRegString(UIntPtr rootKey, string subKey, string name) { UIntPtr hkey; checkErrorCode(NativeMethods.RegOpenKeyEx(rootKey, subKey, 0, NativeMethods.KEY_READ, out hkey)); try { int cbData = 0; checkErrorCode(NativeMethods.RegQueryValueEx(hkey, name, 0, IntPtr.Zero, IntPtr.Zero, ref cbData)); IntPtr ptr = Marshal.AllocHGlobal(cbData); try { checkErrorCode(NativeMethods.RegQueryValueEx(hkey, name, 0, IntPtr.Zero, ptr, ref cbData)); return Marshal.PtrToStringUni(ptr, cbData / sizeof(char)).TrimEnd('\0'); } finally { Marshal.FreeHGlobal(ptr); } } finally { checkErrorCode(NativeMethods.RegCloseKey(hkey)); } } } class Program { static void Main(string[] args) { Console.WriteLine(RegistryWrapper.ReadRegString((UIntPtr)NativeMethods.HKEY_LOCAL_MACHINE, @"HARDWARE\DEVICEMAP\SERIALCOMM", @"\Device\Serial0")); } } } </code></pre> <p><strong>Update</strong></p> <p>It seems that <code>AllocHGlobal</code> and <code>FreeHGlobal</code> are not available on Silverlight. You can p/invoke to <code>LocalAlloc</code> and <code>LocalFree</code> instead. Or you could use <code>CoTaskMemAlloc</code> and <code>CoTaskMemFree</code>. Here's what the former looks like:</p> <pre><code>[DllImport("kernel32.dll", SetLastError=true)] static extern IntPtr LocalAlloc(uint uFlags, UIntPtr uBytes); [DllImport("kernel32.dll", SetLastError=true)] static extern IntPtr LocalFree(IntPtr hMem); </code></pre> <p>Define <code>LMEM_FIXED</code> like this:</p> <pre><code>const uint LMEM_FIXED = 0x0000; </code></pre> <p>Then replace the call to <code>AllocHGlobal</code> with this:</p> <pre><code>IntPtr ptr = LocalAlloc(LMEM_FIXED, cbData); </code></pre> <p>And replace the call to <code>FreeHGlobal</code> with this:</p> <pre><code>LocalFree(ptr); </code></pre>

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